Mechanism of membrane fusion by fusion protein

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In this research project, we have studied to understand the molecular mechanism of viral infectn using influenza fusion peptides. We have particularly focused to determine the structure and orientation of the peptides bund to the membrane. Following results were obtained in this research project.(1) The conformation and dynamics of melittin bound to the dimyristoylphophatidylcholin (DMPC) bilayer and the magnetic orientation in the lipid bilayer systems were investigated by solid-state ^<31>P and ^<13>C NMR spectroscopy. Using ^<31>P NMR, it was found that melittin-DMPC bilayer system forms magnetically oriented elongated vesicles with the long axis parallel to the magnetic field above the liquid crystalline-gel phase transition temperature. ^<13>C NMR spectra were observed on the ^<13>C labeled melittin bound to the lipid bilayers. Finally, it was found that melittin adopts a transmembrane α-helix whose average axis is parallel to the bilayer normal.(2) N-terminal fragment of HA2 (1-27) in influenza virus was synthesized and investigated by solid state NMR spectroscopy. It was found that the N-terminal part of the fragment forms α-helix and showed different behavior of interaction with membrane at acidic pH from that at basic pH condition.(3) Transmembrane fragment of M2 protein of influenza virus (M2-TMP) was synthesized and investigated by means of ^<15>N solid state NMR spectroscopy. The results indicate that the α-helical axis is tilting by 33° and 37° from the bilayer normalin the DOPC and DMPC bilayer systems, respectively.(4) Membran insertion behavior of influenza fusion peptide was investigated by a neutron scattering method. The results indicate that the helical axis is tilting by 55° from the bilayer normal and the helix is located around the surface of bilayers.